This is a great question because it addresses the importance not only of practicing stretching but also the best and safest technique for performing this valuable type of exercise.
Why stretch? Stretching increases flexibility, a key component of physical fitness that is often neglected. A greater degree of flexibility is believed to help prevent injury (and low back pain) and improve sports performance. We lose flexibility as we age, so practicing a regular program of stretching the major muscle groups can help prevent loss of flexibility and its associated negative impact on quality of life in our golden years.
Stretching properly involves a slow, steady elongation of the muscles and tendons to the point of tightness—never pain—and holding the stretch for several seconds. (Never use bouncing or ballistic-type stretching, which can cause injury.) It is best to stretch muscles that have been warmed up internally from exercise as opposed to cold muscles. In fact, stretching cold muscles can actually increase risk of injury, as a cold muscle is more prone to strains! Think of a muscle as if it were a rubber band. If you stretch cold rubber, it snaps and breaks; however, if you warm the rubber first, it stretches more elastically and fluidly, like taffy.
Stretching is different from “warming up.” A warm-up is what you do before you begin a bout of exercise and generally consists of a low-intensity version of the exercise you are planning on engaging in (such as a fast walk before a jog). A good exercise routine would be to warm up (work up a light sweat and raise the internal temperature of your muscles), followed by a series of brief stretches, then perform your exercise bout, warm down and end with another series of stretches. Practice this plan and you will have a well-rounded fitness routine.